This invention relates to novel aminobenzenesulfonic acid derivatives having the activity of inhibiting Ca.sup.2+ overload into cells.
Ca.sup.2+ overload into cells of cardiac muscle or vascular smooth muscle brings about myocardial disorder, conduction disorder or vascular abnormal constriction, etc., and may induce cardiovascular diseases (John A. Watts, American Journal of Physiology, Vol. 238, pp. 909-916 (1980) or Gordon L. Todd, Cardiovascular Research, Vol. 20, pp. 645-651 (1986)).
Therefore, drugs which inhibit Ca.sup.2+ overload into these cells can be useful prophylactic and therapeutical pharmaceuticals for cardiovascular diseases such as ischemic heart diseases, heart failure, hypertension or arrhythmia, etc.
In the prior art, as the drug for inhibiting Ca.sup.2+ overload into cells of cardiac muscle or vascular smooth muscle, there have been known, for example, Ca antagonists or .beta.-adrenoceptor antagonists. However, these drugs, depending on their doses used, have been known to inhibit cardiac function by lowering Ca.sup.2+ concentration within cells in the case of Ca antagonists, or by blocking catecholamine activity in the case of .beta.-blockers, thereby inducing heart failure (Keiji Ueda, Sogo Rinsho, Vol. 36, pp. 851-854 (1987)), and therefore the application to cardiovascular diseases has been limited.